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Diffstat (limited to 'stdlib/random.c')
| -rw-r--r-- | stdlib/random.c | 300 |
1 files changed, 0 insertions, 300 deletions
diff --git a/stdlib/random.c b/stdlib/random.c deleted file mode 100644 index 43bdb1232e..0000000000 --- a/stdlib/random.c +++ /dev/null @@ -1,300 +0,0 @@ -/* Copyright (C) 1995-2017 Free Software Foundation, Inc. - - The GNU C Library is free software; you can redistribute it and/or - modify it under the terms of the GNU Lesser General Public - License as published by the Free Software Foundation; either - version 2.1 of the License, or (at your option) any later version. - - The GNU C Library is distributed in the hope that it will be useful, - but WITHOUT ANY WARRANTY; without even the implied warranty of - MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU - Lesser General Public License for more details. - - You should have received a copy of the GNU Lesser General Public - License along with the GNU C Library; if not, see - <http://www.gnu.org/licenses/>. */ - -/* - * This is derived from the Berkeley source: - * @(#)random.c 5.5 (Berkeley) 7/6/88 - * It was reworked for the GNU C Library by Roland McGrath. - * Rewritten to use reentrant functions by Ulrich Drepper, 1995. - */ - -/* - Copyright (C) 1983 Regents of the University of California. - All rights reserved. - - Redistribution and use in source and binary forms, with or without - modification, are permitted provided that the following conditions - are met: - - 1. Redistributions of source code must retain the above copyright - notice, this list of conditions and the following disclaimer. - 2. Redistributions in binary form must reproduce the above copyright - notice, this list of conditions and the following disclaimer in the - documentation and/or other materials provided with the distribution. - 4. Neither the name of the University nor the names of its contributors - may be used to endorse or promote products derived from this software - without specific prior written permission. - - THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND - ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE - IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE - ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE - FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL - DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS - OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) - HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT - LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY - OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF - SUCH DAMAGE.*/ - -#include <libc-lock.h> -#include <limits.h> -#include <stddef.h> -#include <stdlib.h> - - -/* An improved random number generation package. In addition to the standard - rand()/srand() like interface, this package also has a special state info - interface. The initstate() routine is called with a seed, an array of - bytes, and a count of how many bytes are being passed in; this array is - then initialized to contain information for random number generation with - that much state information. Good sizes for the amount of state - information are 32, 64, 128, and 256 bytes. The state can be switched by - calling the setstate() function with the same array as was initialized - with initstate(). By default, the package runs with 128 bytes of state - information and generates far better random numbers than a linear - congruential generator. If the amount of state information is less than - 32 bytes, a simple linear congruential R.N.G. is used. Internally, the - state information is treated as an array of longs; the zeroth element of - the array is the type of R.N.G. being used (small integer); the remainder - of the array is the state information for the R.N.G. Thus, 32 bytes of - state information will give 7 longs worth of state information, which will - allow a degree seven polynomial. (Note: The zeroth word of state - information also has some other information stored in it; see setstate - for details). The random number generation technique is a linear feedback - shift register approach, employing trinomials (since there are fewer terms - to sum up that way). In this approach, the least significant bit of all - the numbers in the state table will act as a linear feedback shift register, - and will have period 2^deg - 1 (where deg is the degree of the polynomial - being used, assuming that the polynomial is irreducible and primitive). - The higher order bits will have longer periods, since their values are - also influenced by pseudo-random carries out of the lower bits. The - total period of the generator is approximately deg*(2**deg - 1); thus - doubling the amount of state information has a vast influence on the - period of the generator. Note: The deg*(2**deg - 1) is an approximation - only good for large deg, when the period of the shift register is the - dominant factor. With deg equal to seven, the period is actually much - longer than the 7*(2**7 - 1) predicted by this formula. */ - - - -/* For each of the currently supported random number generators, we have a - break value on the amount of state information (you need at least this many - bytes of state info to support this random number generator), a degree for - the polynomial (actually a trinomial) that the R.N.G. is based on, and - separation between the two lower order coefficients of the trinomial. */ - -/* Linear congruential. */ -#define TYPE_0 0 -#define BREAK_0 8 -#define DEG_0 0 -#define SEP_0 0 - -/* x**7 + x**3 + 1. */ -#define TYPE_1 1 -#define BREAK_1 32 -#define DEG_1 7 -#define SEP_1 3 - -/* x**15 + x + 1. */ -#define TYPE_2 2 -#define BREAK_2 64 -#define DEG_2 15 -#define SEP_2 1 - -/* x**31 + x**3 + 1. */ -#define TYPE_3 3 -#define BREAK_3 128 -#define DEG_3 31 -#define SEP_3 3 - -/* x**63 + x + 1. */ -#define TYPE_4 4 -#define BREAK_4 256 -#define DEG_4 63 -#define SEP_4 1 - - -/* Array versions of the above information to make code run faster. - Relies on fact that TYPE_i == i. */ - -#define MAX_TYPES 5 /* Max number of types above. */ - - -/* Initially, everything is set up as if from: - initstate(1, randtbl, 128); - Note that this initialization takes advantage of the fact that srandom - advances the front and rear pointers 10*rand_deg times, and hence the - rear pointer which starts at 0 will also end up at zero; thus the zeroth - element of the state information, which contains info about the current - position of the rear pointer is just - (MAX_TYPES * (rptr - state)) + TYPE_3 == TYPE_3. */ - -static int32_t randtbl[DEG_3 + 1] = - { - TYPE_3, - - -1726662223, 379960547, 1735697613, 1040273694, 1313901226, - 1627687941, -179304937, -2073333483, 1780058412, -1989503057, - -615974602, 344556628, 939512070, -1249116260, 1507946756, - -812545463, 154635395, 1388815473, -1926676823, 525320961, - -1009028674, 968117788, -123449607, 1284210865, 435012392, - -2017506339, -911064859, -370259173, 1132637927, 1398500161, - -205601318, - }; - - -static struct random_data unsafe_state = - { -/* FPTR and RPTR are two pointers into the state info, a front and a rear - pointer. These two pointers are always rand_sep places apart, as they - cycle through the state information. (Yes, this does mean we could get - away with just one pointer, but the code for random is more efficient - this way). The pointers are left positioned as they would be from the call: - initstate(1, randtbl, 128); - (The position of the rear pointer, rptr, is really 0 (as explained above - in the initialization of randtbl) because the state table pointer is set - to point to randtbl[1] (as explained below).) */ - - .fptr = &randtbl[SEP_3 + 1], - .rptr = &randtbl[1], - -/* The following things are the pointer to the state information table, - the type of the current generator, the degree of the current polynomial - being used, and the separation between the two pointers. - Note that for efficiency of random, we remember the first location of - the state information, not the zeroth. Hence it is valid to access - state[-1], which is used to store the type of the R.N.G. - Also, we remember the last location, since this is more efficient than - indexing every time to find the address of the last element to see if - the front and rear pointers have wrapped. */ - - .state = &randtbl[1], - - .rand_type = TYPE_3, - .rand_deg = DEG_3, - .rand_sep = SEP_3, - - .end_ptr = &randtbl[sizeof (randtbl) / sizeof (randtbl[0])] -}; - -/* POSIX.1c requires that there is mutual exclusion for the `rand' and - `srand' functions to prevent concurrent calls from modifying common - data. */ -__libc_lock_define_initialized (static, lock) - -/* Initialize the random number generator based on the given seed. If the - type is the trivial no-state-information type, just remember the seed. - Otherwise, initializes state[] based on the given "seed" via a linear - congruential generator. Then, the pointers are set to known locations - that are exactly rand_sep places apart. Lastly, it cycles the state - information a given number of times to get rid of any initial dependencies - introduced by the L.C.R.N.G. Note that the initialization of randtbl[] - for default usage relies on values produced by this routine. */ -void -__srandom (unsigned int x) -{ - __libc_lock_lock (lock); - (void) __srandom_r (x, &unsafe_state); - __libc_lock_unlock (lock); -} - -weak_alias (__srandom, srandom) -weak_alias (__srandom, srand) - -/* Initialize the state information in the given array of N bytes for - future random number generation. Based on the number of bytes we - are given, and the break values for the different R.N.G.'s, we choose - the best (largest) one we can and set things up for it. srandom is - then called to initialize the state information. Note that on return - from srandom, we set state[-1] to be the type multiplexed with the current - value of the rear pointer; this is so successive calls to initstate won't - lose this information and will be able to restart with setstate. - Note: The first thing we do is save the current state, if any, just like - setstate so that it doesn't matter when initstate is called. - Returns a pointer to the old state. */ -char * -__initstate (unsigned int seed, char *arg_state, size_t n) -{ - int32_t *ostate; - int ret; - - __libc_lock_lock (lock); - - ostate = &unsafe_state.state[-1]; - - ret = __initstate_r (seed, arg_state, n, &unsafe_state); - - __libc_lock_unlock (lock); - - return ret == -1 ? NULL : (char *) ostate; -} - -weak_alias (__initstate, initstate) - -/* Restore the state from the given state array. - Note: It is important that we also remember the locations of the pointers - in the current state information, and restore the locations of the pointers - from the old state information. This is done by multiplexing the pointer - location into the zeroth word of the state information. Note that due - to the order in which things are done, it is OK to call setstate with the - same state as the current state - Returns a pointer to the old state information. */ -char * -__setstate (char *arg_state) -{ - int32_t *ostate; - - __libc_lock_lock (lock); - - ostate = &unsafe_state.state[-1]; - - if (__setstate_r (arg_state, &unsafe_state) < 0) - ostate = NULL; - - __libc_lock_unlock (lock); - - return (char *) ostate; -} - -weak_alias (__setstate, setstate) - -/* If we are using the trivial TYPE_0 R.N.G., just do the old linear - congruential bit. Otherwise, we do our fancy trinomial stuff, which is the - same in all the other cases due to all the global variables that have been - set up. The basic operation is to add the number at the rear pointer into - the one at the front pointer. Then both pointers are advanced to the next - location cyclically in the table. The value returned is the sum generated, - reduced to 31 bits by throwing away the "least random" low bit. - Note: The code takes advantage of the fact that both the front and - rear pointers can't wrap on the same call by not testing the rear - pointer if the front one has wrapped. Returns a 31-bit random number. */ - -long int -__random (void) -{ - int32_t retval; - - __libc_lock_lock (lock); - - (void) __random_r (&unsafe_state, &retval); - - __libc_lock_unlock (lock); - - return retval; -} - -weak_alias (__random, random) |